1. Field of the Invention
The present invention relates to a differential apparatus provided with a differential limiting function or a differential locking function.
2. Description of the Related Art
The Japanese Patent Application Laid-open No. 50(1975)-20331 discloses a differential apparatus with a differential limiting function including a cone clutch, a cam mechanism, an actuator, a stop mechanism and the like.
In the differential apparatus, the differential operation is mechanically limited by the actuator, the stop mechanism and the like. Therefore, a wheel needs to spin at high speed to lock the differential operation, whereby the differential operation cannot be controlled while the vehicle is moving. Specifically, the differential operation cannot be locked or the lock cannot be released in dependence on conditions of vehicle speed, steering, a road surface, or the like.
The actuator and the stop mechanism are composed of a number of parts, such as balances and weights, coil springs of three types, or the like, which are difficult to adjust weight or spring constants thereof, causing unstable motion and variation of products.
Generally, a fluid pressure actuator, such as a pneumatic actuator and a hydraulic actuator or an actuator using an electromagnet, is employed to control the differential operation in dependence on conditions of vehicle speed, steering, and the road surface. Particularly, the fluid pressure actuator is employed because it is capable of generating a large differential limiting force required to lock the differential operation.
However, the fluid pressure actuator needs a pressure source (pump) and a pressure line (piping). Modification or alteration of a casing or a vehicle body for accommodating the differential apparatus is required to make space for arrangement of the pressure source and line. Moreover, it is difficult to unitize, package or modularize the differential apparatus, the pressure source, the pressure line, and the like.
The fluid pressure actuator has low reliability because of possible leak from each portion of the pressure source and line, which causes loss of function. For preventing the leak, seals need to be enforced, thus leading to cost increase.
Meanwhile, in the case of the actuator using an electromagnet, it is difficult to obtain enough differential limiting force to lock the differential operation.
The object of the present invention is to provide a differential apparatus using an electromagnet, in which enough differential limiting force can be obtained to lock differential operation.
Another object of the present invention is to provide a unitized differential apparatus having a differential limiting function, making modification and alteration of a casing or a vehicle body minor or unnecessary.
An aspect of the present invention is a differential apparatus comprising: a rotary input member; a rotary output member within the input member, rotatable relative to the input member; a clutch mechanism for interconnecting the input member and the output member, the clutch mechanism including a first clutch member rotatable together with the input member and a second clutch member rotatable together with the output member, the second clutch member to be axially displaced to engage with the first clutch member; an actuator for limiting rotation of the second clutch member relative to the input member to angularly displace the second clutch member relative to the output member; and a cam mechanism provided between the second clutch member and the output member for engaging the first and second clutch members, the cam mechanism including a first cam face to be rotated together with the second clutch member and a second cam face to be rotated together with the output member, wherein the first and second cam faces cooperate to axially displace the second clutch member away from the output member, as the second clutch member is angularly displaced relative to the output member by the actuator, whereby the second clutch member is axially displaced to engage with the first clutch member.